There are currently several ways to do audio testing of acoustic devices. One of the more common approaches involves generating a signal that is sent to a measurement speaker or artificial mouth, and is then picked up by the device microphone. The signal is looped into the device speaker, where the measurement microphone or artificial ear receives the signal and delivers the signal to the audio analyzer. There are several problems with this method. The signal is passed through four transducers, requiring four electro-acoustic conversions, resulting in distortion of the signal. Additionally, having two speakers and two microphones in one enclosure can cause cross-interference and excess noise.
A second approach, generally known as half-path testing, involves wireless communication with a base station simulator. To test the microphone, a phone call is set-up between a device being tested and the base station simulator. An audio signal is generated in an enclosure and is picked up by the device's microphone. This signal is sent to the base station simulator and measured. The signal at the base station simulator can then be compared to a set of test limits in order to evaluate the quality of the microphone path of the device. To test the speaker, an audio signal is sent by the base station to the device in a phone call. The audio signal that appears on the device speaker can be analyzed and compared to the set of test limits in order to evaluate the quality of the speaker path of the device. This method can be quite expensive, requiring either a base station or a base station simulator. This testing also introduces distortion and noise caused by the signal path from the device to the base station.